This present invention relates to the diamond and jewelry industry and is directed to the need for a means of easily and rapidly identifying man-made gemstone simulants.
Many types of simulated diamonds have been created and are cut to resemble diamond for many reasons. The most common of these simulants have been cubic zirconia, synthetic colorless sapphire, yttrium aluminum garnet (YAG), gadolinium gallium garnet (GGG), synthetic spinel, synthetic rutile and strontium titanate. Although most are for legitimate use in low priced jewelry applications, unfortunately, some are used for fraudulent purposes.
Although most of these simulants are readily detected by persons who have been trained to recognize physical properties such as the refractive index, dispersion of light, hardness and other qualities of the gemstone which differentiate these materials from genuine natural diamond, lay people are easily fooled by these simulants. Until recently, one of the most effective means of detecting simulants was to use a device which could measure the relative thermal conductivity of the simulant materials and compare this property to that of natural diamond. These devices depend upon the fact that diamond conducts heat more rapidly than any of the above materials being cut to resemble diamond.
However, there are other simulants which conduct heat in a similar manner as natural diamond. One of these simulant materials is colorless or near-colorless synthetic diamond grown with the preferred nickel catalyst method. A more recently developed diamond simulant is synthetic moissanite (silicon carbide) which has very similar physical properties as natural diamond. A thermal testing of synthetic moissanite or colorless synthetic diamond will test positive as natural diamond. Additionally, although there are differences in hardness, specific gravity, refractive index and dispersion between natural diamond and moissanite, due to the oftentimes only slight differences in these physical properties even trained professionals have difficulty distinguishing between the two.
Research into the properties of silicon carbide (moissanite) revealed that it was being used in semi-conductor applications which led to the conclusion that differences in resistivity and/or electrical conductance could be detected in the silicon carbide material which could be used as a distinguishing characteristic between natural diamond, with the exception of a very rare type IIB blue diamond, and synthetic moissanite. Accordingly, devices have been produced which attempt to measure the conductivity of synthetic moissanite samples. Testing of moissanite samples further revealed that although silicon carbide was conductive in many cases, there are also samples which are only semi-conductive. Furthermore, the various facets of the moissanite gemstone and the semi-conductive portions of the gemstone create a diodic junction which allows direct current only through certain connecting points of the gemstone. Prior detection devices have utilized high voltage direct current (DC) signals in an attempt to stimulate and detect conductivity by exceeding the reverse breakdown voltage of these junctions. Due to the power requirements, these devices are commonly plugged into an external power source such as a wall outlet. Even with the increased voltage levels, prior moissanite detecting devices must thoroughly probe the gemstone to find conductive connecting points. These points can be quite difficult to find in semi-conductive gemstones, and if not found the tester falsely determines the moissanite sample to be natural diamond.
It has been observed through experimentation that certain man-made gemstones, such as moissanite, exhibit diode-like characteristics when tested with metal probes, and that those characteristics vary in both degree and polarity from sample to sample. It is therefore desirable to employ an alternating current through the gemstone sample to maximize the likelihood of detecting conductive points on such samples.
Therefore, what is needed is a detector for man-made gemstones which can be used to detect synthetic gemstones which cannot be detected by heat conductivity devices. What is also needed is a detector which is unaffected by the diodic effect of man-made gemstones and is able to detect conductivity in conductive and semi-conductive gemstones. Further, a detector is needed which is small, uncomplicated and battery powered. The present invention fulfills these needs and provides other related advantages.